Trigonectes rubromarginatus is seen as a valid species that differs from the close related T. balzanii by the presence of a lower submarginal red band in the caudal fin and other data. The species has a wide range and availability in nature. It can be found in western Brasil in the states Goias, Tocantins and Mato Grosso together with annual species like Maratecoara lacortei, Pituna poranga, Plesiolebias aruana (or Plesiolebias lacerdai, Simpsonichthys costai and Simpsonichthys semiocellatus. Trigonectes rubromarginatus forms a superspecies component together wit T. aplocheiloides, T. balzanii, T. macrophthalmus, T. rogoaguae and T. strigabundus.

Two aquariupopulations are known wich are: Aruana and Cocalinhos. The images to the right were made just after the end of an expedition that was undertaken by R. Wildekamp et al., The Netherlands in 1993 and show the population that came from Cocalinhos.

As all other members of the Trigonectes family they can be found in open landscape with low bushes and in temporary waterbodies. Normally only in deadly waterbodies that have no current. The bottom is mostly build up out of clay in wich the species dives to burry their eggs. This gives us the knowledge the species does not like low pH values lower as neutral and low watertemperatures lower as 25 C. If they do not have any choise Trigonectes lay their eggs not deep into the spawning medium but it is likely they prefer diving into the bottom more than on the bottom.

So they need a high container filled with soft material that is not reacting acid and is deep enough for their large body to dive in. Unlike most other annual species that are no good jumpers Trigonectes can jump occasionally out of the water but it is not likely they jump from pool to pool to find new habitats like rivulus does.

There incubation period can vary between 5 and 12 months, even within one species and an regulary check for development is also needed.

Remarks :

Max. size 12.0 cm.
Dorsal 12.2,
Anal 16.9,
D/A 7.5,
LL scale count (average)38.4
Pre- dorsal length to % SL – 75.3 %
Depth to % SL – 21.5 %